1. Field of the Invention
The present invention relates to a molding apparatus and method of obtaining a glass molded product by press-molding a glass material heated to be deformable.
2. Description of the Related Art
As a conventional glass molding method of obtaining an optical device by pressing a glass material, a general approach is to perform molding by using a set of molds including a pair of upper and lower molds and a mold frame for slidably holding these upper and lower molds. In molding a lens by using this method, it is necessary to prevent a difference between the optical axes of one optical function surface and the other optical function surface and an inclination of the optical axes. To this end, it is necessary not only to accurately finish the mold frame, the upper mold, and the lower mold but also to increase the accuracy with which the mold frame and these molds are assembled.
Since, however, demands on an improvement of the accuracy of press molding of a lens and on reduction in the manufacturing cost are continually increasing, the conventional method cannot satisfy some of these demands. One is the problem of the difference between the optical axes of the two surfaces of a lens or an inclination of the optical axes.
In the above conventional method, for example, the upper and lower molds are slidably incorporated into a hole formed in the mold frame (guide member) for guiding the molds for transferring optical surfaces to a glass material. To increase the optical axis accuracy of a lens, it is necessary to increase the fitting accuracy between the upper and lower molds and the mold frame. However, the improvement of the optical axis accuracy is limited by the processing accuracy of each mold and the high-temperature slidability during pressing.
The upper and lower molds for transferring the optical function surfaces to a glass material are slidably supported by the guide member, and the glass material is inserted between the upper and lower molds and press-molded. If the optical axes of the upper and lower molds, which are originally aligned with each other, produce a parallel shift in the guide member, parallel decentering is produced in the molded lens.
Also, if the upper or lower mold inclines in the fitting gap in the guide member, the optical axes of two optical function surfaces incline.
In Japanese Patent Publication No. 4-21610, the positional relationship between the lower mold and a slide core is maintained because these two members are in contact with each other. However, the upper mold requires a gap so as to be movable in the slide core. Consequently, it is difficult to precisely match the optical axes of the upper and lower molds.
It is, therefore, the first object of the present invention to provide an optical device molding apparatus and method capable of obtaining a glass molded product with high optical axis accuracy.
It is the second object of the present invention to provide an optical device molding apparatus and method capable of more effectively achieving the first object of the present invention with a simpler mold structure.
It is the third object of the present invention to provide an optical device molding apparatus and method capable of obtaining a glass molded product with not only high optical axis accuracy between the two surfaces of an optical device but also high accuracy in the positional relationship between the circumferential surface and the optical axes.
It is the fourth object of the present invention to provide an optical device molding apparatus and method capable of smoothly extracting a molded product without complicating the mold structure.
It is the fifth object of the present invention to provide an optical device molding apparatus and method capable of processing an optical device with any arbitrary shape.
It is the sixth object of the present invention to provide an optical device molding apparatus and method capable of regulating a shift between the optical axes of aspherical optical function surfaces and an inclination of the optical axes.